Radio-interposable data storage media, also known as RFID tags (radio frequency identification tags), are becoming more and more widespread because semiconductor components are becoming cheaper and cheaper. In their simplest form, they are used for security against theft (electronic article surveillance, EAS) as a 1-bit transponder in department stores. They comprise a sticker or label, to which a tuned electric circuit connected to an antenna is fixed. The resonant frequency of the tuned circuit, comprising coil and capacitor, is matched to the frequency of a detection device. As the detection antennas at the exit from the shop are passed, energy is extracted from the electromagnetic field existing between the detection antennas and an alarm is triggered. On the other hand, if the goods have been paid for, by means of an intense magnetic field at the cash desk such a high voltage is induced in the transponder that its capacitor is damaged and therefore the tuned circuit is detuned. When the detection antennas are passed, energy is no longer extracted from the electromagnetic field and, accordingly, no alarm is triggered.
Modern RFID tags are substantially based on the same functional principle but contain in addition semiconductor memories, in which, for example, an identification number is stored. These RFID tags can be read by a reader without contact via radio. Further developments make it possible not only to read data but also to write the RFID tags with data. If RFID tags are equipped with processors which, for example, have cryptographic functions, authentication methods and encryption are even possible.
RFID tags have numerous advantages: they can be read not only without contact but also without a direct line of sight between reader and RFID tag. This is an advantage in particular as compared with the widespread bar code, since RFID tags can still be read even if they are hidden, such as for example under a layer of paint or dirt, in a delivery of a plurality of parts or a package. Furthermore, RFID tags are autonomous, that is to say they can be operated over a period of many years without a battery. They extract the energy needed for operation from the electromagnetic field of the readers. A further advantage of RFID tags is that substantially more data can be stored in them than, for example, in bar codes.
The advantages of RFID tags lead to diverse and innovative possible applications. If articles are identified with RFID tags, then, for example, automatic monitoring of sales racks is possible. As soon as the last unit has been sold, the store personnel are requested to fill the rack again. If fitted in items of clothing, RFID tags can provide an intelligent washing machine with tips about the type of cleaning to be selected. A shopping cart which is filled with articles identified with RFID tags could simply be pushed past a reader at the cash desk, the prices being registered by radio. However, the use of RFID tags in logistics is of particular economic importance. With the aid of an electronic product code (EPC), which allocates a unique number worldwide to each article, RFID tags make efficient and automated product processing possible in delivery chains which cover the world. For example, all the individual parts of a pallet load could be inspected without any visual connection, given appropriate marking with RFID tags. However, a precondition for this is that, even in the case of identical articles, each article is given an individual number. If the possibility of writing RFID tags is also provided, then in addition to the point of origin, transport routes and storage conditions can additionally be traced back and, in this way, the entire chain comprising manufacturer, seller and final purchaser can be monitored. The possible savings in work and time as a result of using RFID tags are enormous.
However, pilot trials with RFID tags in large retail concerns have met with resistance from civil liberty and data protection activists. Amongst other things, there is a fear that the RFID tags will be read unnoticed and without the knowledge of the consumer. This is important in particular if an article which is identified uniquely worldwide is linked with personal data, such as that which is transmitted when payment is made with a credit card. If this link is followed, then, for example, a movement profile could be drawn up and, by using RFID tags on other articles, a purchasing behavior could be determined. Shoes which are provided with RFID tags could be read at every entry provided with a reader. Clothing which contains RFID tags can be read not only by the washing machine but also by a reader fitted by an employer at the place of work and used to monitor the employees. The consumer would thus become a transparent consumer and able to be monitored. The offer to destroy the RFID tags at the cash desk and thus to prevent misuse is mistrusted, since the consumer has no possibility of distinguishing between permanently deactivated and temporarily silenced (sleep mode) tags.